1. Field of the Invention
The invention concerns a process for fine and micro-machining of workpieces using laser beams as well as a device for carrying out the process. This type of process and device has already been proposed.
2. Description of the Related Arts
The fine and micro-machining of workpieces using laser beams, in particular laser drilling and laser ablation, is employed for example for production of function-optimized fine drilling or for forming three-dimensional surface structures. A non-exhaustive list of possible applications includes for example:
cooling holes and in certain cases form bore holes in turbine blades,
perforations of thin sheet metal, for example, for boundary layer suction removal,
lubrication bore holes in motors and transmissions,
spray openings in injector nozzles,
precision cuts in materials which are difficult to mill,
micro-structures in sliding and rolling surfaces.
Essential for the qualitatively high value of the fine and micro-machining of workpieces by means of laser beams is above all a good as possible precision of dimension and shape, a precise as possible reproducibility and a low as possible follow-up processing expenditure.
These requirements are only unsatisfactorily accomplished by the known processes and devices.
In U.S. Pat. No. 5,632,083 a method and an apparatus are described for fabricating a lead frame. In the apparatus the workpiece is irradiated with a laser beam. The apparatus includes a device for focusing the laser beam, a device for rotating the laser beam about the beam axis, and a device for variation of the point of impact of the laser beam on the workpiece.
Besides this there exist for example processes and devices, in which the laser beam is guided for example by means of a Trepanier optic system. A disadvantage thereof is the limited possibility of the shaped defined thereby; only round bore holes or structures are possible. A defined conicity of the bores or structures cannot be selected.
In other known processes and devices, the workpiece is moved by means of an x-y-table or, in another variant, also by means of a robot. The disadvantage therein is that the workpiece must be moved, and it has been found in practice that the track precision of the workpiece movement is worse than that of a guided laser beam and as a consequence the size and shape precision of the laser processing is comparatively poor.
In other known processes and devices, the deflection of the laser beam occurs exclusively by means of an x-y-scanner. A disadvantage therein is that the path precision has been found to be worse and the size and shape stability of the laser processing resulting therefrom is comparatively poor. Beyond this, it is not possible to provide a defined conicity of the bore or structure.
In other previously known processes and devices, the deflection of the laser beam occurs by means of a moveable robot-guided cutting optic. A disadvantage therein is that, here also, as has been found in practice that there is a lower path precision, and the therefrom resulting size and shape precision of the laser processing is comparatively poorer.
Beyond this, in all the above-discussed processes and devices an asymmetric intensity distribution of the laser beam results in the production of asymmetric cut seams.
The task of the present invention is comprised therein, of providing a process and a device for fine and micro-machining of workpieces by means of laser beams, which partially or completely
produces cut seams or notches with substantially equivalent dimensional shapes,
permits a substantially free selection of shape during processing,
makes possible an adjustment of the desired conicity,
works with high precision and reproducibility.
The invention provides a process and device are disclosed for fine and micro-machining workpieces by means of laser beams. The process is conducted in several stages and the device has a modular design. The process and device make it possible to generate highly uniform cut seams or grooves, to set the required conicity, to work in a highly accurate and reproducible manner and give a great freedom of design during machining.
With respect to the process for fine and micro-processing of workpieces by means of laser beams, the task is inventively solved thereby,
that the laser beam is guided through three modules prior to reaching the workpiece, and thereby
that in the first module the laser beam is rotated about its beam axis, and
that by means of the second module the impact point of the laser beam upon the work piece is varied, and
that by means of the third module the incident angle of the laser beam relative to the surface of the workpiece is varied.
The task is inventively solved, with respect to the device for fine and micro-machining of workpieces by means of laser beams, thereby,
that the device is comprised of three modules,
of which the first contains a device for rotation of the laser beam about its transmission axis, and
the second contains a device for variation of the point of impact of the laser beam upon the workpiece, and
the third contains a device for variation of the incident angle of the laser beam relative to the surface of the workpiece.
The advantage of such a construct of the process and device is comprised therein, that by the rotation of the laser beam about its rotation axis a variation in the intensity distribution and/or an unround focusing can be compensated for, and therewith an even cut seam results during the processing of the workpiece, and therein, that the variation of the point of impact of the laser beam makes possible a wide as possible unrestricted selection of the shape during processing, and therein, that the variation of the incident angle of the laser beam makes possible an adjustment or selection of a desired conicity.
In an advantageous embodiment of the invention concerning the device for fine and micro-machining of workpieces by means of laser beams, the module for rotation of the laser beams contains one or more prisms, which receive the optical beam axis and cause an image rotation, preferably a Dove-, Abbe-, or King prism, as well as a device for rotation thereof or the prism about a rotation axis, and a device for controlling a defined rotational speed of the rotation.
The advantage of this design is comprised therein, that the laser beam can be homogenized with respect to its cross-sectional geometry and/or intensity (time averaged) and this without influencing the impact point or the impact angle of the laser beam on the workpiece, and without reducing the quality of the form-producing processing.
In an advantageous embodiment of the invention concerning the device for fine and micro-machining of workpieces by means of laser beams, the module for variation of the impact point of the laser beam includes a mirror, as well as a device for rotation of the mirror about at least two independent rotation axis, preferably perpendicular rotation axes, whereby the device for rotation of the mirrors preferably includes piezo actuators.
The advantage of this design is comprised therein, that with it the laser beam can be deflected in such a manner, that the production of highly precise and reproducible workpiece geometries is made possible, in particular also the production of rotation asymmetric geometries or the ablation of three-dimensional structures on the workpiece outer surface. The perpendicular arrangement of the rotation axis simplifies the setting up of defined deflections of the laser beam. The piezo actuators make possible the achievement of an optimal precision.
In another advantageous embodiment of the invention concerning the device for fine and micro-machining of workpieces by means of laser beams, the module for variation of the impact point of the laser beam contains multiple mirrors or other deflection devices, as well as devices for rotation of the mirror about at least two independent rotation axes, preferably perpendicular rotation axis, wherein preferably respectively one mirror is rotated about respectively one rotation axis, and wherein the devices for rotation of the mirror preferably include piezo actuators.
The advantage of this design corresponds to that of the embodiment described immediately above.
In an advantageous embodiment of the invention concerning the device for fine and micro-machining of workpieces by means of laser beams, the module for variation of the impact angle of the laser beam includes a device for rotation of the overall module about the beam axis of the incident beam, a device fixed within the module for deflection of the incident laser beam in the plane perpendicular to the incident beam direction, preferably containing multiple fixed mirrors or a fixed prism, as well as a further device for deflection of the laser beam, which is moveable within the module, preferably in the form of a mirror or a prism, as well as a device for translation of this moveable deflection device along the broadcast direction of the laser beam emitted from the fixed deflection device, as well as a device for tilting of the moveable deflection device about at least one further axis.
The advantage of this design is comprised therein, that by the rotation of the complete module circular bore holes can be produced, and therein, that by the translation and the tipping or tilting of the moveable deflection device it becomes possible to select any desired radius of the bore and any desired inclination or cone angle of the bore.
In a further advantageous embodiment of the invention concerning the device for fine and micro-machining of workpieces by means of laser beams, the module for variation of the impact angle of the laser beam contains a device for deflection of the laser beam in two independent directions (x-y-deflection), preferably released in the form of two independent scanner-mirrors, as well as two associated devices for rotation of the scanner-mirrors about two independent axis, preferably about two axis oriented perpendicularly to each other.
The advantage of this design is comprised therein, that thereby also circular bore holes with adjustable radius and adjustable conicity can be produced. The difference with respect to the first-described variant is comprised therein, that the first can be employed for extremely fine bore holes in the micrometer realm, while the second permits the working of substantially larger geometries and angles.
In a further advantageous embodiment of the invention concerning the device for fine and micro-machining of workpieces by means of laser beams, there is situated between the second module for variation of the impact point of the laser beam and the third module for variation of the impact angle of the laser beam a further deflection device, preferably in the form of a mirror.
The advantage of such a deflection is in the possibility of changing the work plane, for example, from a vertical processing of the workpiece to a horizontal processing.